PL194685B1 - Compositions crystalline propylene copolymer of improved bonding ability, improved optical properties and reduced dissolvability - Google Patents

Abstract

A crystalline propylene copolymer composition having MFR L values from 2 to 15 g/10 min. and comprising (percent by weight): A) 20-80 % of one or more propylene copolymers; B) 20-80 % of one or more propylene copolymers with different comonomer(s) content than in A); the said MFR L values (MFR L (2)) being obtained by subjecting to degradation a precursor composition comprising the same components A) and B) in the above said proportions, but having MFR L values (MFR L (1)) from 0.3 to 5 g/10 min., with a ratio MFR L (2) to MFR L (1) of from 2 to 20.

Description

Description of the invention

The present invention relates to a crystalline propylene copolymer composition, a method of its preparation and its use. The crystalline propylene copolymer compositions are useful in the preparation of hot seal films and films and sheets made therefrom.

Crystalline copolymers of propylene with other olefins (mainly ethylene, 1-butene or both), or mixtures of such copolymers with other olefin polymers, are known in the art as heat bonding materials. These crystalline copolymers are obtained by polymerizing propylene with minor amounts of other olefin comonomers in the presence of coordination catalysts.

The polymerized comonomer units are distributed statistically in the resulting copolymer, and the melting point of such copolymers becomes lower than that of the crystalline propylene homopolymers. Also, the welding initiation temperature (as defined in detail hereinafter) for the copolymers mentioned turns out to be advantageously low.

However, the incorporation of comonomer units adversely affects the crystalline structure of the polymer, leading to a relatively large amount of organic solvent-soluble polymer fractions, so that copolymers exhibiting a particularly low sealing initiation temperature cannot be used in the food packaging field.

The prior art discloses many technical solutions to find a good compromise between heat sealability (characterized by low sealing initiation temperatures) and solubility. In particular, EP 483 523 discloses compositions prepared directly by the polymerization process having a low sealing initiation temperature and a low xylene soluble fraction at room temperature or in hexane at 50 ° C. These compositions contain (by weight):

30-60% of a copolymer of propylene and a C4-C8 alpha-olefin containing 80-98% of propylene;

35-70% of a copolymer of propylene with ethylene and optionally 1-10% of a C4-C8-alpha-olefin, where the ethylene content is 5-10%, when the polymer does not contain C4-C8-alpha-olefin or 0.5-5% when C4-C8-α-olefin is contained in the polymer.

The application EP 674 991 discloses other compositions produced directly by the polymerization process with good ink adhesion, additionally with a low sealing initiation temperature and a low content of the polymer fraction soluble in organic solvents.

These compositions contain (by weight):

20-60% of a propylene-ethylene copolymer containing 1 to 5% of ethylene;

40-80% of a copolymer of propylene with ethylene and a C4-C8-alpha-olefin wherein the ethylene content is 1-5% and the content of C4-C8-alpha-olefin is 6-15%;

wherein the total ethylene content of the composition is 1-5% and the total C4-C8 alpha-olefin content is 2.4-12%.

Other heat sealable compositions containing two different types of propylene copolymers with higher alpha-olefins are disclosed in EP 560 326.

On the other hand, it is generally known that the melt flow rate (MFR) of an olefin polymer can be adjusted by degradation, in particular by treatment at elevated temperatures in the presence of free radical initiators (rough cracking treatment).

It is also known in the field of heat-bonding olefin copolymers that said degradation treatment can improve heat-bondability, optical properties and solubility, as explained in particular in US Patent 5,246,769 and published Japanese Patent Application Sho 59-117506.

In these two documents, however, the degradation treatment was applied to single copolymers of propylene with ethylene and / or a higher alpha-olefin, leading to a still high seal initiation temperature.

An attempt to apply the degradation treatment to heat sealable compositions containing two copolymers of propylene with ethylene and / or higher alpha-olefins is disclosed in EP 203 727. In this case, a copolymer of propylene with 25-45% by weight of butene-1 is first treated by degrading and then mixing with another propylene-ethylene and / or butene-1 copolymer.

However, although the welding initiation temperature and the haze values have been adjusted to a satisfactory level, the content of the fraction soluble in organic solvents

Remains high (xylene soluble fraction at 25 ° C of approx

30% is considered satisfactory).

US 5,326,625 discloses multi-layer films with a high degree of whiteness and opacity, in which the top layer is 0.4 mm or less thick. It has been shown in the examples that such a layer can be made of a peroxide degraded ethylene / propylene copolymer. In contrast, there is no disclosure or even suggestion in the present document that by degrading the blend of copolymers it might be possible to achieve highly transparent materials having a valuable balance between heat welding suitability and a low organic solvent soluble fraction.

It has surprisingly been found that a particularly valuable compromise between heat welding properties, low organic solvent soluble fraction and optical properties (in particular very low haze) is obtained by subjecting particular crystalline propylene copolymer compositions to degradation treatment.

The crystalline propylene copolymer composition with MFR L values of 2 to 15 g / 10 minutes, according to the invention, is characterized by containing, in percent by weight

A) 20-60% of one or more propylene copolymers selected from the group consisting of (A1) propylene / ethylene copolymers containing 1-7% ethylene and (A3) propylene-ethylene copolymers and one or more C4- _C8 -alpha olefins containing 0.5-4.5% ethylene and 2-6% C4- _C8 -alpha-olefins, provided that the total content of ethylene and C4-C8-alpha-olefins in (A3) is equal to or less than 6.5%;

B) 40-80% of one or more propylene copolymers selected from the group consisting of (B2) propylene-ethylene copolymers and one or more C4-C8-α-olefins containing 1-7% ethylene and 6-15% C4-C8 - alpha-olefins, said MFR L (MFR 1 (2)) being obtained by degrading a precursor composition containing the same components A) and B) in the above-mentioned proportions but showing MFR L (MFR L (1) values) ) from 0.3 to 5 g / 10 minutes, and the ratio of MFR L (2) to MFR L (1) is from 2 to 20.

Preferably, the composition comprises, by weight percent

A) 20-60% propylene / ethylene copolymer containing 1-7% ethylene;

B) 40-80% of a propylene-ethylene copolymer and one or more C4-C8-α-olefins, containing 1-7% ethylene and 6-15% C4-C8-α-olefins, with the total ethylene content of the composition being 1 -5%, and the total C4-C8-α-olefin content of the composition is 2.4-12%.

The use of a crystalline propylene copolymer composition as defined above according to the invention is characterized in that the composition is used for the production of a monolayer or multilayer film or sheet.

A method for producing a crystalline propylene copolymer composition, as defined above, comprising the step 1) preparing a precursor composition by polymerizing the monomers in at least two sequential steps, wherein components A) and B) are produced in separate, successive steps carried out in each step in the presence of the polymer produced in the previous step and the catalyst used in the previous step and with the dosing of the molecular weight regulator in such amounts as to obtain an MFR L (1) value for the precursor composition in the range of 0.3 to 5 g / 10 minutes, according to the invention is characterized by in that the precursor composition obtained in step 1) is processed by degradation in the next step 2) in order to obtain the MFR L (2) value for the final composition ranging from 3 to 15 g / 10 minutes, the degradation ratio being defined as the ratio MFR L (2) to MFR L (1) is from 2 to 20.

Preferably, the degradation ratio is from 3 to 15.

The present invention thus provides crystalline propylene copolymer compositions with MFR L values of 2 to 15 g / 10 minutes, preferably 3 to 15 g / 10 minutes, and more preferably 4 to 10 g / 10 minutes.

MFR L (MFR L (2)) values are obtained by degrading a precursor composition containing the same components A) and B) in the above-mentioned proportions but having MFR L (MFR L (1)) values of 0.3 to 5 g / 10 min, preferably from 0.5 to 3 g / 10 min, and the ratio of MFR L (2) to MFR L (1) is from 2 to 20, preferably from 3 to 15. From the above definitions it is clear that the term " copolymer "includes polymers containing more than one type of comonomer.

PL 194 685 B1

As previously mentioned, the compositions according to the invention exhibit low sealing initiation temperatures (preferably lower than 100 ° C), low levels of organic soluble or extractable fractions (preferably equal to or lower than 20 wt% in xylene at 25 ° C and equal to or less than 5% by weight in n-hexane at 50 ° C) and very low haze values (preferably less than 1%, more preferably less than 0.5%, measured on the film according to the method described in the examples).

The melting point of this composition is preferably from about 126 to 147 ° C.

Moreover, the compositions according to the invention can be obtained by an effective and economical process, which is - as already mentioned - also an object of the invention and includes the steps discussed above.

As a molecular weight regulator, hydrogen is preferably used in such amounts as to give an MFR L (1) value for the precursor composition in the range of 0.3 to 5 g / 10 minutes, preferably 0.5 to 3 g / 10 minutes.

The precursor composition obtained in step 1) is subjected to degradation treatment to obtain MFR L (2) values for the final composition ranging from 3 to 15 g / 10 minutes, preferably from 4 to 10 g / 10 minutes, the degradation ratio being referred to as the ratio of MFR L (1) to MFR L (2) is from 2 to 20, preferably from 3 to 15.

Such a preferred method is extremely convenient as it avoids the separate preparation of the components of the precursor composition and the separate treatment by degradation.

It should be clear from the preceding description that the comonomer content of the precursor composition and the relative amounts of components A) and B) in the precursor composition and in the final composition (after degradation) are the same. The treatment by degradation increases the composition MFR L size from MFR L (1) to MFR L (2), with the ratio between the two MFR L values, namely MFR L (2) / MFR L (1) being from 2 to MFR L (1). 20. The above-mentioned MFR L values are measured according to ASTM D 1238 L.

Both in the precursor composition and in the final composition, the MFR L values for both components A) and B) are not particularly critical as long as the MFR L value for the total composition is within the aforementioned range.

Indicatively, the MFR L values for both A) and B) may be 0.1-10 g / 10 minutes in the precursor composition.

The recommended comonomer content of the composition according to the invention is (by weight):

- 2-4% ethylene for (A1);

- 1-4% of ethylene and 2-5% of one or more C4-C8 alpha-olefins, with a total content of ethylene and C4-C8 alpha-olefins equal to or lower than 6% for (A3);

1-4% ethylene and 2-5% one or more C4-C8 alpha-olefins for (B2).

Moreover, when optimal ink adhesion is desired, the compositions of the invention should contain component (A1) and component (B2) in the aforementioned relative amounts, while the total ethylene content of the composition should be 1-5%, preferably 2-4% by weight and the total content of C4-C8 alpha-olefins should be 2.4-12%, preferably 3.5-8.4% by weight.

Examples of C4-C8-α-olefins are 1-butene, 1-pentene, 1-hexene, 4-methyl-pentene and 1-octene. 1-butene is particularly recommended.

As previously explained, the precursor compositions can be prepared by sequential polymerization. Such polymerization is carried out in the presence of stereospecific Ziegler-Natta catalysts. An essential component of said catalysts is a solid catalyst component comprising a titanium compound with at least one titanium-halogen bond, an electron donor compound, both applied to a magnesium halide support in active form. Another essential component (co-catalyst) is an organoaluminum compound, such as an aluminum alkyl compound.

An external donor is optionally added.

The catalysts generally used in the process of the invention lead to the production of polypropylene with an isotactic index greater than 90%, preferably greater than 95%. Catalysts having the above properties are well known in the patent literature; the catalysts described in US Patent 4,399,054 and European Patent 45,977 are particularly preferred.

The solid catalyst components used in these catalysts contain as electron donating compounds (internal donors) compounds selected from ethers, ketones, lactones, compounds containing N, P and / or S atoms and esters of mono- and dicarboxylic acids.

PL 194 685 B1

Phthalic acid esters such as diisobutyl phthalate, dioctyl phthalate, diphenyl phthalate and benzyl butyl phthalate are particularly suitable.

Other particularly suitable electrode donors are 1,3 diethers of the formula:

wherein R ¹ and R ¹¹ , same or different, are C 1 -C 18 alkyl, C 3 -C 18 cycloalkyl or C 7 -C 18 aryl radicals, R ¹¹¹ and R ^IV , same or different, are C 1 -C 4 alkyl radicals; or are 1,3 diethers wherein the carbon atom in position 2 belongs to a cyclic or polycyclic structure containing 5, 6 or 7 carbon atoms and containing two or three unsaturated bonds.

Ethers of this structure are described in published European patent applications EP-A-361493 and 726769.

Representative examples of said compounds are: 2-methyl-2-isopropyl-1,3-dimethoxypropane, 2,2-diisobutyl-1,3-dimethoxypropane, 2-isopropyl-2-cyclopentyl-1,3-dimethoxypropane, 2-isopropyl- 2-isoamyl-1,3-dimethoxypropane and 9,9-bis (methoxymethyl) fluorene.

The preparation of the above-mentioned catalyst components is carried out by various methods.

For example, an adduct of MgCl4. NROH (especially in the form of spherical particles) where n generally varies from 1 to 3 and the ROH is ethanol, butanol, isobutanol, is reacted with an excess of TiCl ₄ containing the electron donor compound. The reaction temperature is generally from 80 to 120 ° C. The solid is then separated and reacted once more with TiCl 2, with or without an electron donor, then separated and washed repeatedly with hydrocarbon until the chloride ion disappears.

The titanium compound, expressed as Ti, in the solid catalyst component is generally present in a percentage ranging from 0.5 to 10% by weight. The amount of electron donor compound retained on the solid component (internal donor) generally ranges from 5 to 20 mol% with respect to magnesium dichloride.

The titanium compounds that can be used in the preparation of the solid catalyst component are titanium halides and haloalkoxides. A preferred compound is titanium tetrachloride.

The reactions described above lead to the formation of a magnesium halide in active form.

Other reactions are known in the literature to produce a magnesium halide in active form, starting from magnesium compounds other than halides, such as magnesium carboxylates.

The active form of magnesium halide in the solid catalyst component can be recognized by the fact that in the X-ray spectrum of the catalyst component the maximum intensity reflection appearing in the spectrum of the nonactivated magnesium halide (with a surface area smaller than 3 m ² / g) is no longer is no longer present, but in its place there is a halo with the maximum intensity shifted from the position of the maximum reflection intensity of the unactivated magnesium dihalide or by the fact that the maximum reflection intensity has a half height width of at least 30% greater than the maximum reflection intensity appearing in the spectrum of the unactivated magnesium halide. The most active forms are those where the above-mentioned halo appears in the X-ray spectrum of the solid catalyst component.

Among the magnesium halides, magnesium chloride is preferred. In the case of the most active form of magnesium chloride, the X-ray spectrum of the solid catalyst component shows halo instead of the reflection which appears at 2.56 × 10 m in the spectrum of the unactivated chloride.

Al-Alkyl Compounds used as cocatalysts include trialkyl Al compounds such as triethyl Al, triisobutyl Al, tri-n-butyl Al and linear or cyclic Al Alkyl compounds having two or more Al atoms bonded to each other O or N, or SO4 or SO _{3 groups} .

The Al-alkyl compound is generally used in amounts such that the Al / Ti ratio ranges from 1 to 1000.

Electron donating compounds which can be used as external electron donors include aromatic esters such as alkyl benzoates, and in particular silicone compounds, containing at least one Si-OR bond, in which R is a hydrocarbon radical.

PL 194 685 B1

Examples of silicone compounds are (t-butyl) 2-Si (OCH3) 2, (cyclohexyl) (methyl) Si (OCH3) 2, (phenyl) 2Si (OCH3) 2 and (cyclopentyl) 2Si (OCH3) 2. 1,3-diethers of the formulas described above can also be used advantageously. If the internal donor is one of the diethers mentioned, the external donor may be omitted.

As previously mentioned, the polymerization step may be carried out in at least two successive steps for producing components A) and B) in separate successive steps for each step except the first step, in the presence of the polymer formed and the catalyst used in the previous stage. The catalyst is only added in the first step, but is active in such a way that it is retained in the following steps.

The order of manufacture of components A) and B) is not critical.

The polymerization step, which can be carried out continuously or in batch mode, is carried out by known techniques and takes place in a liquid phase, with or without an inert diluent, or in a gas phase, or in a liquid-gas phase. It is preferable to carry out the polymerization in a gas phase.

Reaction time, pressure and temperature in these two steps are not critical, however, a temperature of from 20 to 100 ° C is most preferred. The pressure may be atmospheric or elevated. The regulation of the molecular weight is carried out with the aid of known regulators, hydrogen in particular.

The catalyst may be pre-contacted with a small amount of olefins (prepolymerization).

Specific examples of precursor compositions suitable for the preparation of the compositions of the invention by degradation treatment and polymerization process for the preparation of said precursor compositions are disclosed in the already cited European patent applications 483523, 560326 and 674991.

The degradation treatment may be carried out by any method and conditions known in the art effective to reduce the molecular weight of the olefin polymers.

In particular, it is known that the molecular weight of olefin polymers can be reduced by the use of heat (thermal degradation), preferably in the presence of free radical initiators, and ionizing radiation or chemical initiators.

Among the chemical initiators, organic peroxides are particularly preferred, a particular example of which are 2,5-dimethyl-2,5-di (butylperoxy) hexane and dicumyl peroxide.

The degradation treatment with chemical initiators can be carried out in conventional equipment generally used for melt processing plastics, as well as in specific single or twin screw extruders. It is preferable to work under an inert atmosphere, for example under a nitrogen atmosphere.

The amount of chemical initiator added to the precursor composition can be readily determined by one skilled in the art based on the MFR L (1) values (i.e. the MFR L value for the precursor composition) and the desired MFR L (2) value (i.e. the MFR L value for the final composition). Generally, such amounts range from 100 to 700 ppm.

The degradation temperature is preferably in the range from 180 to 300 ° C.

The compositions according to the invention may also contain various additives commonly used in the art, such as antioxidants, light stabilizers, heat stabilizers, dyes and fillers.

Among the various possible applications that take advantage of the previously described properties, the compositions of the invention are particularly useful in the production of sheets and films.

The films generally have a thickness of less than 100 mm, while the sheets are generally greater than 100 mm in thickness. Both films and sheets can be single-layer and multi-layer. In the case of multilayer films or sheets, at least one layer comprises the compositions of the invention. Each layer which does not contain the composition of the invention may be composed of other olefinic polymers such as polypropylene or polyethylene.

Generally speaking, the films and sheets of the invention can be produced by known methods such as extrusion and calendering. Particular examples of films containing the compositions of the invention are those disclosed further in the Sealing Initiation Temperature (S.I.T.) tests.

Details are given in the following examples which are given for the purpose of illustration and are not intended to limit the present invention.

PL 194 685 B1

Examples 1 and 2 (comparative)

In the following example 1, a precursor composition is produced by sequential polymerization and then degraded to obtain the final composition. For comparison purposes, in Example 2 a composition is produced directly by polymerization with a heat start temperature lower than 100 ° C and an MFR L value comparable to that obtained in Example 1 by degradation.

The solid catalyst component used for the polymerization is the highly specific component of the Ziegler-Natta catalyst applied to a magnesium chloride support containing about 2.5% by weight of titanium and diisobutyl phthalate as internal donor, prepared analogously to the process described in published European patent application 674991.

Catalyst system and prepolymerization treatment

Prior to introduction into the polymerization reactor, the solid catalyst component described above is contacted at -5 ° C for 5 minutes with triethylaluminum (TEAL) and dicyclopentyldimethoxysilane (DCPMS) at a TEAL / DCPMS weight ratio of about 4 in such amounts that the molar ratio TEAL / Ti is 65.

The catalyst system is then prepolymerized by keeping it in suspension in liquid propylene at 20 ° C for about 20 minutes before feeding it into the first polymerization reactor.

Polymerization

In the first gas-phase polymerization reactor, a propylene / ethylene copolymer (component (A)) is prepared by introducing at a constant and continuous flow a prepolymerized catalyst system, hydrogen (used as a molecular weight regulator) and ethylene and propylene gas monomers.

The polymerization conditions, the molar proportions of the reactants and the composition of the composition obtained are shown in Table 1.

The copolymer produced in the first reactor, constituting 35% by weight of the total composition of Example 1 and 40% by weight of the total composition of Example 2, is continuously discharged and, after purification of unreacted monomers, is continuously introduced into the second gas phase reactor along with with steady streams of hydrogen and gaseous propylene, ethylene and 1-butene monomers.

The propylene / ethylene / 1-butene copolymer formed in the second reactor (component (B)) was produced in an amount of 65% by weight based on the total composition of Example 1 and 60% by weight based on the total composition of Example 2.

The polymerization conditions, the molar proportions of the reactants and the composition of the composition obtained are shown in Table 1.

The polymer particles exiting the second reactor are treated with steam to remove unreacted monomers and volatiles, and then dried.

The polymer particles are then introduced into a rotating drum where they are mixed with 0.05% by weight of ROL / OB 30 paraffin oil (density 0.842 kg / l at 20 ° C according to ASTM D 1298 and -10 ° C according to ASTM D 97), 0.15 wt.% Irganox B 215 (containing about 66 wt.% Tri [2,4-di-t-butyl-phenyl] phosphite and a balance to 100% in the form of tetrakis [methylene (3.5 -di-t-butyl-4-hydroxy-hydroxycinnamate)]) and 0.05% by weight of calcium stearate.

Also, 300 ppm of Luperox 101 (2,5-dimethyl-2,5-di (t-butylperoxy) hexane) was added to the part of the polymer molecules of Example 1, which was the precursor composition, which acts as a free radical initiator in the following treatment in extruder.

The polymer particles are then introduced into a Berstorff ZE 25 twin screw extruder (screw length / diameter ratio is 33) and extruded under a nitrogen atmosphere under the following conditions:

rotation speed: 200 bbr. for min.

extruder capacity: 6-20kg / h, melt temperature: 200-250 ^:: C.

The data relating to the polymer composition reported in Tables 1 and 2 are obtained from measurements carried out on the polymers so extruded. The data reported in Table 2 relates to the final composition according to the invention, obtained by degradation of the precursor composition

Of Example 1, namely by extruding it with the addition of 300 ppm of Luperox 101 as described above.

The data in the tables were obtained using the following test methods.

The molar ratio of the feed gases

Determined by gas chromatography.

Ethylene and 1-butene content in polymers

Determined by infrared spectroscopy.

Melt flow rate MFR L

The L conditions are determined according to ASTM D 1238.

Melting point (Tm) and crystallization temperature (Tc)

Determined by DSC (Differential Scanning Calorimetry)

Xylene soluble fraction

Determined as follows.

about

2.5 g of polymer and 250 cm of xylene are introduced into a glass flask equipped with cooling and a magnetic stirrer. The temperature is raised in 30 minutes up to the boiling point of the solvent. The thus obtained clear solution is kept under reflux and stirred for a further 30 minutes. The closed flask is then kept for 30 minutes in an ice-water bath and in a thermostatic water bath at 25 ° C also for 30 minutes. The solid thus formed is filtered through a quick-drain filter. 100 cm ^{3 of the} filtered liquid is poured into a previously weighed aluminum container which is heated on a heating plate under nitrogen in order to remove the solvent by evaporation. The container is then kept in an oven at 80 ° C under vacuum until constant weight is obtained.

Hexane soluble fraction

It is determined according to FDA 177, 1520, by suspending in excess hexane a 100 mm thick film sample from the composition to be analyzed in an autoclave at 50 ° C for 2 hours. The hexane is then removed by evaporation and the dried residue is weighed.

Welding start temperature (S.I.T.)

It is defined as follows.

Production of a foil sample

Some 50 mm thick films were produced by extruding each test composition in a Collin single screw extruder (screw length / diameter ratio: 25) with a film draw speed of 7 m / min and a melt temperature of 210-250 ° C. Each resulting film is applied to a 1000 mm thick propylene homopolymer film having an isotacticity index of 97 and an MFR L of 2 g / 10 min. The superimposed films are bonded in a Carver press at 200 ° C under a load of 9000 kg held for 5 minutes.

The obtained laminate is stretched longitudinally and transversely, i.e. biaxially, by a factor of 6 on a TM Long film stretcher at 150 ° C, thus obtaining films with a thickness of 20 mm (18 mm homopolymer + 2 mm test composition).

Samples with dimensions of 2 x 5 cm are cut from the foil.

Determination of S.I.T.

In each test, two of the above samples are stacked longitudinally, with the adjacent layers constituting the individual test compositions. The superimposed samples are welded along one of the 5 cm long sides using a Brugger Feinmechanik Sealer, model HSG-ETK 745. The sealing time is 0.5 seconds under a pressure of 0.1 N / mm ² . The sealing temperature is increased for each seal starting at a temperature 10 ° C below the melting point of the test composition. The welded specimens are allowed to cool and then their non-welded ends are clamped in an Instron machine where they are tested at a feed rate of 50 mm / min.

The S.I.T. temperature is the minimum sealing temperature at which the seal will not crack under a load of at least 2 Newtons under the test conditions mentioned.

Cloudy foil

Determined on a 50 mm thick film of the test composition, prepared as described for the S.I.T. The measurement is carried out on a 50 x 50 mm section cut from the central zone of the foil.

The instrument used is a Gardner photometer with a Hazemeter UK-10 turbidity apparatus equipped with a GE 1209 lamp and a C filter. The instrument is calibrated by

Measurement in the absence of sample (0% haze) and measurement with an interrupted beam of light (100% haze).

The gloss of the foil

It is determined for the same sample as for turbidity.

The test apparatus used is a model 1020 Zehntner photometer for measuring the incident light. Calibration is carried out by measuring at an incidence angle of 60 ° on black glass with a standard gloss of 96.2% and measuring at an angle of incidence of 45 ° on black glass with a standard gloss of 55.4%.

Table 1

Examples 1 2 (comparative) 1st reactor Temperature, ° C 70 70 Pressure, MPa 1.8 1.6 H2 / C3, moles <0.01 0.04 ^C 2 ^{/ C} 2 + ^C 3 ^{, mole} 0.03 0.03 Polymer obtained C ^2- % 3.1 3.1 MFR L, g / 10 min 0.54 5.0 2nd reactor Temperature, ° C 65 65 Pressure, MPa 1.6 1.6 H2 / C3, moles 0.21 0.13 C ^{2 /} C ² + C ^{3, mole} 0.03 0.03 ^C4 ' ^{/ C4} ' + C ³ - mote 0.17 0.17 Total composition C ^2- % 4.0 4.0 C ^4- % 6.0 5.8 MFR L, g / 10 min 0.98 4.4 Tm / Tc, ° C 136 / 88.7 134 / 87.7 X. S.% 11.9 15.1 H. S.% 3.9 7.0 C2 ^at Χ.Ι _Μ % 3.2 - C4 ⁱⁿ Χ.Ι.% 5.6 - C2 ⁱⁿ XS _M % 10.9 - C ^{4 in XS} . % 8.9 - S. I. T., ° C 97 97 Turbidity,% 11.9 1.9 Gloss, ° / oo 66.2 80.0

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Table a 2 (example 1)

Complete comyozyyja C-% 4.0 CT,% 6.0 MFR L, g / 10 min 5.7 Tm / Tc, ° C 137 / 89.9 X.S. % 11.9 H.S. % 3.8 C ₂ 'in Χ.Ι. % 3 CT in Χ.Ι. % 4.6 C ₂ 'W XS% 6.6 C ^{4 in XS} . % 9.8 S. I. T., ° C 93 Turbidity,% 0.1 Gloss, ° / _Μ 88.5

Notes on tables

C2 = ethylene, C3 '= propylene, C4' = 1-butene, X.S = xylene soluble fraction, H.S = hexane soluble fraction, X.I = xylene insoluble fraction H.S = hexane insoluble fraction; all percentages are by weight (except turbidity).

Comparing the data in Table 2 and the data for Comparative Example 2 reported in Table 1, it appears that a compromise of S.I.T, low solubility and optical properties of the compositions of the invention is not obtained when a comparable MFR L value is obtained directly during polymerization.

Claims (5)

Patent claims 1. Crystalline co-polymer composition with MFR L values ranging from 2 to 15 g / 10 minutes, characterized in that it contains, in percent by weight, A) 20-60% of one or more propylene copolymers selected from the group consisting of (A1) propylene / ethylene copolymers containing 1-7% ethylene and (A3) propylene-ethylene copolymers and one or more C4- _C8 - alpha- olefins, containing 0.5-4.5% of ethylene and 2-6% C 4 -C ₈ - alpha-olefins, provided that the total content of ethylene and _C4-C8 - alpha-olefins in (a 3) is equal to or less than 6.5%; B) 40-80% of one or more propylene copolymers selected from the group consisting of (B2) propylene-ethylene copolymers and one or more C4-C8-α-olefins containing 1-7% ethylene and 6-15% C4-C8 - alpha-olefins, said MFR L (MFR 1 (2)) being obtained by degrading a precursor composition containing the same components A) and B) in the above-mentioned proportions but showing MFR L (MFR L (1) values) ) from 0.3 to 5 g / 10 minutes, and the ratio of MFR L (2) to MFR L (1) is from 2 to 20. 2. Kc ^ re ^ r ^^ n ^ ^c ^ j ^ l of the crystalline propylene polymer mound according to the principles. The composition of claim 1, comprising, by weight percent A) 20-60% propylene / ethylene copolymer containing 1-7% ethylene; B) 40-80% of a copolymer of propylene with ethylene and one or more C4-C8- alpha-olefins, containing 1-7% ethylene and 6-15% C4-C8- alpha-olefins, The total ethylene content of the composition is 1-5% and the total C ₄ -C ₈ α-olefin content of the composition is 2.4-12%. 3. The use of a crystalline propylene copolymer defined in z ^^ tr ^^. 1 for producing a single-layer or multi-layer film or sheet. 4. A method for producing k (^ ι ^ | ^ (^^^ <ci propylene copdlmer as defined in 1, comprising step 1) making a precursor composition by polymerizing monomers in at least two consecutive steps wherein components A) and B) are produced in separate, successive steps carried out in each step in the presence of the polymer produced in the previous step and the catalyst used in the previous step and dosing the molecular weight regulator in such amounts to obtain the MFR L (1) value for the precursor composition ranging from 0.3 to 5 g / 10 minutes, characterized in that the precursor composition obtained in step 1) is processed by degradation in the next step 2) in order to obtain the MFR L (2) value for the final composition ranging from 3 to 15 g / 10 minutes, the degradation ratio defined as the ratio of MFR L (2) to MFR L (1) is from 2 to 20. 5. The method according to p. The process of claim 4, wherein the degradation ratio is from 3 to 15.